1. Field of the Invention
The invention is directed generally to an axial piston machine having a swash plate construction with a cylindrical drum that is connected to a shaft. The shaft passes through the swash plate and is supported on one end against a control surface. The drum has a number of concentrically located elongated cylindrical passages formed therein and each passage has a longitudinally moveable piston therein. Each piston is provided at one end with a sliding shoe that is in working connection with the swash plate and which has a sliding shoe plate and a sliding shoe neck. The faces of the sliding shoe plates opposite from the swash plate contact an annular spring-loaded hold-down plate that is provided with concentrically located recesses corresponding in number and spacing with the cylindrical passages in the cylindrical drum to receive the sliding shoe necks.
2. Description of Related Prior Art
An axial piston machine generally in accordance with the above description is known from German Patent No. DE 3222210. The hold-down plate described therein is spring-loaded and prevents the slide shoes from rising under the action of the inertial forces and the suction forces of the swash plate on the piston during rotation of the cylindrical drum. The spring force is designed to handle the maximum forces that arise during operation of the machine, but the force also operates in normal operation with lower loads. Thus, during normal operation there is the disadvantage of high friction between the slide shoes and the swash plate and this is especially true when a machine starts from a dead stop. In order to eliminate this shortcoming, the above-referenced patent suggests that the hold-down or retaining plate or at least the annular portion thereof acts on the latter with a spring action against a stop connected with the drive shaft. This arrangement results in the force of the spring being transferred to the stop rather than to the slide shoe, at least when the machine is stopped. The spring is to act on the slide shoe through the annular part and the retaining plate and prevent it from rising further only when the slide shoe rises past a predetermined degree. In order to assure proper functioning of an axial piston machine designed in this manner, it is necessary to maintain very precise tolerances in the production and assembly of the elements.